In the past, in the operation for arrangement of reinforcements in construction work, for example, the tying and securing of portions of reinforcements placed one above another have been generally carried out by manual operation. An iron wire is bent in advance into two parts so as to have a U-shape. The U-shaped wire is extended over a portion of reinforcements placed one above another. A hook portion of a jig, called a twist shaft is hung on a bent portion of the iron wire and is then rotated several times to twist opposite ends of the iron wire to each other to bind the portions placed one above another. To obtain the positive tying, great skill and heavy labor is required, resulting in poor operating efficiency. Thus, mechanization therefor has been demanded.
Further, a tying machine for automatically tying reinforcements has been proposed. However, tying machines thus proposed suffer from a problem in that any one of these machines is complicated in construction, is heavy in weight, is high in manufacturing cost, and is inconvenient in handling. Further, in any one of these conventional machines, a single iron wire is drawn out of a bobbin and wound around a joined portion of reinforcements with that single iron wire to bind the joined portion, and therefore it is necessary to wind the object several times in order to provide a firm tying. A long tying material is required as compared with the tying through manual operation, resulting in a higher cost of tying materials. A further problem is that the single wire tends to be ruptured, and a strong tying force is hard to obtain as compared with the tying through manual operation for effecting the tying after the iron wire is bent into two parts to form a double configuration.
For solving the above-described problems, the present inventors have previously proposed a method and an apparatus therefor for automatically bending a continuous linear tying material drawn out of a bobbin or similar to form two wires to provide powerful tying by a single winding (International Application International Laid-Open Publication No. WO95/05313).
The tying method and the tying apparatus therefor, proposed as described above, are further improved by the present invention. It is an object of the present invention to provide a tying method and a tying apparatus therefor which is simple in mechanism, is less in the number of parts, is light-weight, is less in load imposed on a motor to prolong the service life of the motor, and can firmly and positively tie articles by a short tying material as compared with the prior art.